The present invention relates to a variable-flow curve element for a transfer system for transporting products, in particular for transporting workpiece holders on which the products are disposed.
In assembly, for instance, workpieces are conveyed from work station to work station by means of a transfer system. As the conveying means, often two constantly revolving parallel tracks are used, on which workpiece holders that hold workpieces are transported. Depending on the layout of the transfer system, curves or 180° deflections must also be provided. As curve elements for such transfer systems, so-called roller curves are for instance known, in which there are many rollers disposed side by side, the rollers extending over the full width of the track. The two tracks end upstream of the curve element and are deflected upstream of the curve element.
Another way of attaining a known curve element is to provide a round belt as the conveying means on the inside of the curve. On the outside of the curve, only a guide is provided. As a result, the workpiece holders are moved around the curve only by means of the driven round belt.
The two known curve elements described above have the disadvantage, however, that congestion cannot be allowed on the curve, because the workpiece holders can easily become jammed there, which thus interrupts transport onward. Moreover, especially with the round belt, if the workpiece holders become congested, excessively high wear would occur, which would significantly shorten its service life. In these known curve elements, it must therefore be assured that the workpiece holders pass through individually. This requires major effort and expense for control technology and moreover has an adverse effect on the shortest possible cycle time.
It is also known for the two tracks to be guided continuously through the curve by means of a curve-going roller chain. However, since the radius of the curve-going tracks is very limited, with such an embodiment only a long curve radius can be achieved, which adversely affects the space requirement and hence possible system layouts. Hence the use of this so-called double-track curve element is quite limited.